Fludarabine, cyclophosphamide and anti-thymocyte globulin for alternative donor transplants in acquired severe aplastic anemia: a report from the EBMT-SAA Working Party

The state of the art in the treatment of severe aplastic anemia: immunotherapy and hematopoietic cell transplantation in children and adults

Acquired aplastic anemia (AA) is an immune-mediated bone marrow (BM) failure where marrow disruption is driven by a cytotoxic T-cell-mediated autoimmune attack against hematopoietic stem cells. The key diagnostic challenge in children, but also in adults, is to exclude the possible underlying congenital condition and myelodysplasia. The choice of treatment options, either allogeneic hematopoietic cell transplantation (alloHCT) or immunosuppressive therapy (IST), depends on the patient's age, comorbidities, and access to a suitable donor and effective therapeutic agents. Since 2022, horse antithymocyte globulin (hATG) has been available again in Europe and is recommended for IST as a more effective option than rabbit ATG. Therefore, an update on immunosuppressive strategies is warranted. Despite an improved response to the new immunosuppression protocols with hATG and eltrombopag, some patients are not cured or remain at risk of aplasia relapse or clonal evolution and require postponed alloHCT. The transplantation field has evolved, becoming safer and more accessible. Upfront alloHCT from unrelated donors is becoming a tempting option. With the use of posttransplant cyclophosphamide, haploidentical HCT offers promising outcomes also in AA. In this paper, we present the state of the art in the management of severe AA for pediatric and adult patients based on the available guidelines and recently published studies.

Co-transplantation of umbilical cord mesenchymal stem cells and peripheral blood stem cells in children and adolescents with refractory or relapsed severe aplastic anemia

To evaluate the co-transplantation efficacy of umbilical cord mesenchymal stem cells (UC-MSCs) and peripheral blood stem cells (PBSCs) as a novel approach for refractory or relapsed severe aplastic anemia (R/R SAA) in children and adolescents, thirty-two children and adolescents diagnosed with R/R SAA underwent a retrospective chart review. The patients were categorized into two groups based on the source of PBSCs: the matched sibling donor (MSD) group and the unrelated donor (UD) group. No adverse events related to UC-MSC infusion occurred in any of the patients. The median time for neutrophil engraftment was 13 days (range: 10-23 days), and for platelets, it was 15 days (range: 11-28 days). Acute GVHD of Grade I-II and moderate chronic GVHD were observed in 21.8 and 12.5% of cases, respectively. No statistically significant differences were found between the MSD and UD groups in terms of engraftment, GVHD, and complications, including infection and hemorrhagic cystitis. The median follow-up time was 38.6 months (range: 1.4-140.8 months). As of October 31, 2021, five patients had succumbed, while 27 (84.4%) survived. The 5-year OS rate showed no statistically significant difference between the MSD and UD groups (84.8 ± 10.0 vs. 82.4 ± 9.2%, p = 0.674). In conclusion, the application of UC-MSCs in the treatment of R/R SAA in PBSC transplantation is reliable and safe, they had no graft rejection, low incidence of severe GVHD which may have been contributed by the co-infusion of MSC.

Autologous hematopoietic recovery after allogeneic hematopoietic stem cell transplantation: A case-based review

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is widely applied for the treatment of hematologic malignancies, but autologous hematopoietic recovery (AR) after allo-HSCT is rare clinically, especially after myeloablative conditioning (MAC). The mechanism of AR remains unclear so far, but the prognosis for most patients is relatively good. Second transplantation is preferred after disease relapse. Starting from a real-life clinical case scenario, herein we reviewed some of the crucial issues of AR in light of recent refinements, and discussed our patients based on the current evidence.

Shifting Paradigms: The Case of Autologous Reconstitution after an Upfront Matched Unrelated Hematopoietic Cell Transplantation for Severe Acquired Aplastic Anemia in a Child

During the last few years, the therapeutic landscape of idiopathic aplastic anemia (IAA) has been profoundly revolutionized by the increased use of alternative transplant procedures, such that today hematopoietic cell transplantation (HCT) from a matched unrelated donor (MUD) has been suggested as a possible first line strategy in pediatric patients with severe IAA, in the absence of a matched related donor. However, in this particular context, outcomes and early and long-term toxicities remain to be determined, as compared to non-transplant procedures. While prospective trials are ongoing, we report here the case of a 12-year-old boy with IAA, receiving an upfront bone marrow HCT from a MUD, who experienced early graft rejection associated with autologous hematological recovery, which could induce remission of his hemopathy. This case offers the opportunity to discuss the challenges associated with these new transplant paradigms and provides a brief review of the literature regarding the issue of autologous recoveries after allogeneic HCT in IAA.

Human leucocyte antigen-matched related haematopoietic stem cell transplantation using low-dose cyclophosphamide, fludarabine and thymoglobulin in children with severe aplastic anaemia

When human leucocyte antigen-matched related donors are available, haematopoietic stem cell transplantation (HSCT) in children with severe aplastic anaemia (SAA) represents the standard of care. Cyclophosphamide (Cy) 200 mg/kg and anti-thymocyte globulin (ATG) are frequently administered, but to-date, no standard conditioning regimen exists. In this study, we investigated the efficacy of a unified HSCT conditioning protocol consisting of low-dose Cy 80 mg/kg, fludarabine and ATG. Data were reviewed from children aged ≤14 years with either acquired SAA or non-Fanconi anaemia inherited bone marrow failure syndrome (IBMFS) between 2011 and 2022 at various Saudi institutions. Graft-versus-host disease (GVHD) prophylaxis included mycophenolate mofetil and calcineurin inhibitors. HSCT was performed in 32 children (17 females and 15 males). Nine patients had deleterious mutations (two ERCC6L2, two ANKRD26, two TINF2, one LZTFL1, one RTEL1 and one DNAJC21). Four patients had short telomeres. All 32 patients engrafted successfully. At 3 years post-transplant, the event-free survival was 93% and overall survival was 95%. Two patients experienced secondary graft failure or myelodysplastic syndrome. A low probability of GVHD was observed (one acute GVHD II and one mild chronic GVHD). These data highlight how HSCT using low-dose Cy as part of a fludarabine-based regimen is safe and effective in SAA/non-Fanconi anaemia IBMFS.

Safety and Efficacy of Co-transplantation of Hematopoietic Stem Cells Combined With Human Umbilical Cord-Derived Mesenchymal Stem Cells in Children With Severe Aplastic Anemia: A Single-Center Experience

OBJECTIVES

The mostimportant problems thatlimitthe effectiveness of allogeneic hematopoietic stem cell transplantation in patients with severe aplastic anemia are graft failure and graft-versus-host disease. Mesenchymal stem cells can support normal hematopoiesis and prevent graft-versus-host disease. We aimed to analyze the effects of combined transplant of human umbilical cord-derived mesenchymal stem cells and matched donor allogeneic hematopoietic stem cells in children with severe aplastic anemia.

MATERIALS AND METHODS

We retrospectively examined 15 pediatric patients with severe aplastic anemia who received fludarabine-based reduced intensity conditioning regimen and intravenously infused human umbilical cord-derived mesenchymal stem cells at a dose of 1 × 106/kg recipient body weight within 12 to 18 hours before hematopoietic stem cells infusion. We evaluated the engraftment rate, the frequency and severity of graft-versus-host disease, and the overall survival rate.

RESULTS

No patients had adverse events related to intravenously human umbilical cord-derived mesenchymal stem cells infusion. All patients achieved successful engraftment and sustained donor chimerism. The median time for neutrophil and platelet engraftment was 14 and 25 days,respectively. The frequency was 20% for grade III/IV acute graftversus- host disease and 15.3% for chronic graftversus-host disease. Patients were followed-up for a median of 33 months (range, 2-89 months). The 5-year overall survival rate was 80%.

CONCLUSIONS

Combined transplant of matched donor hematopoietic stem cells with human umbilical cord-derived mesenchymal stem cells is safe in pediatric patients with severe aplastic anemia. The achievement of engraftment in all of our patients and the acceptable frequency of acute and chronic graft-versus-host disease and survival rate are encouraging.

Fludarabine/Cyclophosphamide Conditioning Regimen in Aplastic Anemia Patients Receiving Matched-Sibling Donor Transplant Is Non-inferior to ATG/Cyclophosphamide: A Single-Center Experience from Pakistan

The successful outcome of allogeneic hematopoietic stem cell transplant (HSCT) in aplastic anemia patients is driven by suitable donor selection, appropriate conditioning regimen, early intervention, and optimal supportive care after transplant. Pakistan, being a developing country, faces grave economic challenges due to meager health care budget; therefore, cost constraints remain the foremost impediment in optimizing transplant facilities for socioeconomically deprived patients. We conducted a single-center retrospective analysis of aplastic anemia patients (N = 130), who received matched sibling donor transplants from 2011 to 2019, treated with either fludarabine/cyclophosphamide (Flu/Cy) or antithymocyte globulin/cyclophosphamide (ATG/CY) conditioning regimen. Median age was 16 years (IQR, 11-20), and it ranged from 3 to 48 years. The median time from diagnosis to transplant was 3 months (IQR, 2 to 4), and it ranged from 1 to 8 months. The estimated overall survival (OS), relapse-free survival (RFS), and GvHD-free survival (GFS) were found to be 69.0%, 66.7%, and 64.3% in the ATG/Cy group while 76.1%, 72.7%, and 62.5% in the Flu/Cy group, respectively, after a median follow-up of 30 months (IQR, 8 to 55), and it ranged from 0 to 98 months for the study groups. The Flu/Cy regimen was well tolerated and was not associated with increased risk of GvHD. Hence, it may be an appropriate alternative conditioning regimen for developing countries with limited health care resources.

First-line haploidentical stem cell transplantation in children and adolescents with severe aplastic anemia using mobilized peripheral blood as source of CD34+: Single-institutional experience in a transplant center from northeast Mexico

INTRODUCTION

The only curative treatment for severe aplastic anemia in children is an allogeneic stem cell transplant; however, few patients have a matched related or unrelated donor. Haploidentical stem cell transplantation (haplo-SCT) using bone marrow (BM) and peripheral blood stem cells (PBSC) has been recently described as effective and safe. In this study, we retrospectively report the outcome of twelve pediatric patients who underwent haplo-SCT using only PBSC.

METHODS

The conditioning regimen consisted on rabbit anti-thymocyte globulin (r-ATG) 2.5 mg/kg/d on days -7, -6,-5, and -4, and cyclophosphamide (Cy) 50 mg/kg/d on days -3 and -2. We used Cy 50 mg/kg/d on days +3 and +4, tacrolimus and mycophenolic acid as graft versus host disease (GVHD) prophylaxis.

RESULTS

The median follow-up was 1,099 days (45-1258 days). The overall survival rate up-to-date is 83.3%. In 10 of the 12 patients, a sustained graft was achieved. None of the patients had acute or chronic GVHD.

CONCLUSIONS

Haplo-SCT could be established as a first-line treatment when there is no matched related or unrelated donor. According to this short sample and previous reports, PBSC are a feasible option effectively used as the sole source of stem cells. Additionally, post-transplant cyclophosphamide remains a good strategy for GVHD prevention.

Fludarabine-Cyclophosphamide-Based Conditioning with Antithymocyte Globulin Serotherapy Is Associated with Durable Engraftment and Manageable Infections in Children with Severe Aplastic Anemia

Severe aplastic anemia (SAA) is a bone marrow failure syndrome that can be treated with hematopoietic cell transplantation (HCT) or immunosuppressive (IS) therapy. A retrospective cohort of 56 children with SAA undergoing transplantation with fludarabine-cyclophosphamide-ATG-based conditioning (FluCyATG) was analyzed. The endpoints were overall survival (OS), event-free survival (EFS), cumulative incidence (CI) of graft versus host disease (GVHD) and CI of viral replication. Engraftment was achieved in 53/56 patients, and four patients died (two due to fungal infection, and two of neuroinfection). The median time to neutrophil engraftment was 14 days and to platelet engraftment was 16 days, and median donor chimerism was above 98%. The overall incidence of acute GVHD was 41.5%, and that of grade III-IV acute GVHD was 14.3%. Chronic GVHD was diagnosed in 14.2% of children. The probability of 2-year GVHD-free survival was 76.1%. In the univariate analysis, a higher dose of cyclophosphamide and previous IS therapy were significant risk factors for worse overall survival. Episodes of viral replication occurred in 33/56 (58.9%) patients, but did not influence OS. The main advantages of FluCyATG include early engraftment with a very high level of donor chimerism, high overall survival and a low risk of viral replication after HCT.

Bone marrow transplantation for acquired aplastic anemia: What's new

Bone marrow transplantation is a major therapeutic option for patients with acquired severe aplastic anaemia: improved survival has been achieved in younger patients, thanks to better donor selection, conditioning regimens and graft versus host disease prophylaxis, together with improved supportive care, including diagnosis and treatment of opportunistic infections. This has not been the case for older patients over the age of 40 years. We will discuss transplantation platforms as used for different donor types and we will analyse major breakthroughs of the last years: the combination of Fludarabine and cyclophosphamide as a conditioning regimen, the use of alternative donors including HLA haploidentical related donors and new strategies to prevent acute and chronic graft versus host disease, including post transplantation Cyclophosphamide. These changes extend the option of a bone marrow transplantation for patients who lack an HLA matched donor and appear to improve engraftment and reduce graft versus host disease: whether this will be true for all age groups is currently being investigated.

Hematopoietic stem cell transplantation for inherited bone marrow failure syndromes: alternative donor and disease-specific conditioning regimen with unmanipulated grafts

Objective: The outcomes of alternative donor hematopoietic stem cell transplantation (HSCT) with unmanipulated grafts for Inherited bone marrow failure syndromes (IBMFS) are discouraging. Our study is to demonstrate that IBMFS with disease-specific characteristics requires a tailored conditioning regimens to enhance engraftment and reduce regimen related toxicities. Methods: We retrospectively analyzed 42 patients diagnosed with IBMFS and transplanted with an alternative donor graft at our center from November 2012 to August 2018. Twenty-seven patients had Fanconi anemia (FA), 7 had dyskeratosis congenita (DC), and 8 had severe congenital neutropenia (SCN). Patients received ex-vivo unmanipulated alternative donor grafts from a matched unrelated donor (MUD) (n = 22), haploidentical donor (HID) (n = 17) and unrelated cord blood donor (UCBD) (n = 3). FA and DC patient subgroups received reduce intensified conditioning (RIC), while SCN patients received a myeloablative conditioning (MAC) regimen. Results: The median follow-up time for the surviving patients was 38 months (range: 9-63 months). The failure-free survival (FFS) for entire cohort was 76.1%, and was 72.4%, 100% and 56.2% for patients with FA, DC and SCN, respectively. There were no primary graft failures. The cumulative incidence of aGVHD at day 100 was 48.1%. The cumulative incidence of cGVHD at 1 and 3 years was 35.0% and 69.3%, respectively. Conclusion: HSCT using alternative donors with unmanipulated grafts and disease-specific conditioning regimens for IBMFS patients shows promising survival.

Choice of conditioning regimens for bone marrow transplantation in severe aplastic anemia

Allogeneic bone marrow transplantation (BMT) is curative therapy for the treatment of patients with severe aplastic anemia (SAA). However, several conditioning regimens can be used for BMT. We evaluated transplant conditioning regimens for BMT in SAA after HLA-matched sibling and unrelated donor BMT. For recipients of HLA-matched sibling donor transplantation (n = 955), fludarabine (Flu)/cyclophosphamide (Cy)/antithymocyte globulin (ATG) or Cy/ATG led to the best survival. The 5-year probabilities of survival with Flu/Cy/ATG, Cy/ATG, Cy ± Flu, and busulfan/Cy were 91%, 91%, 80%, and 84%, respectively (P = .001). For recipients of 8/8 and 7/8 HLA allele-matched unrelated donor transplantation (n = 409), there were no differences in survival between regimens. The 5-year probabilities of survival with Cy/ATG/total body irradiation 200 cGy, Flu/Cy/ATG/total body irradiation 200 cGy, Flu/Cy/ATG, and Cy/ATG were 77%, 80%, 75%, and 72%, respectively (P = .61). Rabbit-derived ATG compared with equine-derived ATG was associated with a lower risk of grade II to IV acute graft-versus-host disease (GVHD) (hazard ratio [HR], 0.39; P < .001) but not chronic GVHD. Independent of conditioning regimen, survival was lower in patients aged >30 years after HLA-matched sibling (HR, 2.74; P < .001) or unrelated donor (HR, 1.98; P = .001) transplantation. These data support Flu/Cy/ATG and Cy/ATG as optimal regimens for HLA-matched sibling BMT. Although survival after an unrelated donor BMT did not differ between regimens, use of rabbit-derived ATG may be preferred because of lower risks of acute GVHD.

Conditioning regimen for allogeneic bone marrow transplantation in children with acquired bone marrow failure: fludarabine/melphalan vs. fludarabine/cyclophosphamide

Fludarabine/cyclophosphamide-based conditioning regimens are standard in bone marrow transplantation (BMT) for acquired bone marrow failure in children, however, graft failure may occur. Using the data from a nationwide transplantation registry, we compared the outcomes of children aged <16 years with acquired aplastic anemia and refractory cytopenia of childhood who underwent allogeneic BMT with either fludarabine/melphalan (n = 71) or fludarabine/cyclophosphamide (n = 296) between 2000 and 2016. The fludarabine/melphalan regimen provided excellent outcomes, with 3-year overall survival and failure-free survival rates of 98% and 97%, respectively. The 83% 3-year failure-free survival in the fludarabine/cyclophosphamide group was significantly inferior (P = 0.002), whereas the overall survival did not differ between the two groups. Late graft failure was the most common cause of treatment failure in the fludarabine/cyclophosphamide group, which experienced a significantly higher incidence of late graft failure than the fludarabine/melphalan group (11% vs. 3%; P = 0.035). Multivariate analyses showed that the fludarabine/melphalan regimen was associated with a better failure-free survival (hazard ratio [HR] 0.12; P = 0.005) and lower risk of late graft failure (HR 0.16; P = 0.037). Fludarabine/melphalan-based conditioning regimen can be a promising option for children with acquired bone marrow failure receiving BMT.

Successful treatment with matched unrelated donor peripheral blood stem cell transplantation for very severe aplastic anemia in presence of active infections: A case report

RATIONALE

Very severe aplastic anemia (vSAA) with active infections is always fatal. Adequate infection control before hematopoietic stem cell transplantation is recommended.

PATIENT CONCERNS

A 38-year-old woman with vSAA suffered from acute perforated appendicitis and invasive pulmonary fungal infection, and she failed to respond to intense antimicrobial therapies.

DIAGNOSIS

She was diagnosed with refractory vSAA with stubborn acute perforated appendicitis and invasive pulmonary fungal infection.

INTERVENTIONS

We successfully completed an emergent reduced intensity conditioning-matched unrelated donor (MUD)-peripheral blood stem cell transplantation (PBSCT) as a salvage therapy in the presence of active infections. The conditioning regimens consisted of reduced cyclophosphamide 30 mg/kg/day from day-5 to day-3, fludarabine 30 mg/m/day from day-5 to day-3 and porcine-antilymphocyte immunoglobulin 15 mg/kg/day from day-4 to day-2 without total body irradiation. Cyclosporin A, mycophenolate mofetil and short-term methotrexate were administered as graft-versus-host disease (GVHD) prophylaxis. Neutrophils and platelets were engrafted on day+15 and day+21. Appendiceal abscess and severe pneumonia developed after neutrophil engraftment, which were successfully managed with intense antimicrobial therapy and surgical intervention.

OUTCOMES

Only limited cutaneous chronic GVHD was observed 5 months after transplantation. The patient still lives in a good quality of life 2 years after transplantation.

LESSONS

Active infections may be no longer a contraindication to hematopoietic stem cell transplantation for some patients with vSAA.

Allogeneic hematopoietic stem cell transplantation for aplastic anemia with pre-transplant conditioning using fludarabine, reduced-dose cyclophosphamide, and low-dose thymoglobulin: A KSGCT prospective study

The optimal pre-transplant conditioning for aplastic anemia (AA) remains unclear. We performed a prospective study on allogeneic transplantation from a related or unrelated donor for adult patients with AA. We assessed whether reduced-dose cyclophosphamide (CY) could decrease toxicity while maintaining engraftment, and low-dose thymoglobulin could safely prevent graft-vs-host disease (GVHD). The pre-transplant conditioning regimen consisted of fludarabine 120 mg/m² , CY 100 mg/kg, and thymoglobulin 2.5 mg/kg with or without 2 Gy of total body irradiation. Twenty-seven patients with a median age of 36 years were analyzed. Sixteen patients received graft from related donors. The stem cell source was bone marrow in 26 patients. All of the patients but one, who died early, achieved neutrophil engraftment at a median of 19 days. Mixed chimerism was observed in six and five patients at days 30 and 90, respectively. Only one patient experienced secondary engraftment failure with complete donor-type chimerism. None of the patients developed severe acute GVHD. The cumulative incidence of chronic GVHD was 37.7% at 1 year. The overall survival rate was 96.3% at 1 year and 3 years. A high EB virus-DNA load was detected in one patient at days 60. No one developed EBV-lymphoproliferative disorder within a year. The results suggest that the conditioning regimen in this study was safe and effective. However, relatively high incidence of chronic GVHD needs further improvement.

Clinical impact of anti-thymocyte globulin on survival and graft-versus-host disease in patients undergoing human leukocyte antigen mismatched allogeneic stem cell transplantation

BACKGROUND/AIMS

Rabbit anti-thymocyte globulin (ATG) is usually incorporated in hematopoietic stem cell transplantation (HSCT) to reduce the incidence of graft-versus-host disease (GVHD). This study aimed to find optimal ATG doses in patients undergoing human leukocyte antigen (HLA)-mismatched allogeneic HSCT.

METHODS

We retrospectively collected medical records from 352 consecutive patients with acute myeloid leukemia (n = 214), acute lymphoblastic leukemia (n = 62), or myelodysplastic syndrome (n = 76) in eight centers of Korea between 2005 and 2015. All patients received busulfan-based conditioning without total body irradiation (TBI) and received stem cells from HLA-mismatched donors.

RESULTS

In the current study, 5-year overall survival rates of patients receiving low to medium doses of ATG (2.5 to 7.5 mg/kg) were higher than those receiving other doses of ATG (hazard ratio [HR], 0.528; 95% confidence interval [CI], 0.311 to 0.897; p = 0.018). The incidence rates of extensive chronic GVHD (ecGVHD) after administration of low to medium doses of ATG were lower than those after other doses of ATG (HR, 0.447; 95% CI, 0.224 ton 0.889; p = 0.022).

CONCLUSION

The low to medium doses of ATG may be associated with improving survival outcomes and reducing incidence of ecGVHD without enhancing the chances of relapse in patients with acute leukemia or myelodysplastic syndrome undergoing non-TBI-based HLA-mismatched allogeneic HSCT.

Allogeneic Bone Marrow Transplants for Pediatric Severe Aplastic Anemia: Real-world Data comparing Matched Related and Unrelated Donors in a Developing Country. Retrospective study on behalf of the Pediatric Hematopoietic Stem Cell Transplant Working Group of the Brazilian Bone Marrow Transplantation Society (SBTMO) and the Brazil-Seattle Consortium (Gedeco)

In this study, we report on major MRD or URD BMT outcomes in pediatric patients with SAA in Brazil. This was a retrospective study, which included 106 patients ≤18 years old who received a first BMT for SAA. All patients received bone marrow as graft source from an MRD (n = 69) or a URD (n = 37). Conditioning regimen was non-myeloablative in 73.6% of cases, and GVHD prophylaxis comprised a calcineurin inhibitor plus methotrexate in 89.6% of patients. After a median follow-up of 4.5 years after BMT, 81 patients are alive, with a 4-year OS of 77% and no statistically significant difference between the MRD and URD groups (82% vs. 69%, respectively; P = .08). Grade III-IV aGVHD at 6 months and cGVHD at 2 years were observed in 8% and 14% of cases, respectively, and were not statistically different between the groups. Twenty-five (23%) patients died at a median of 2.9 months after BMT. Our study showed that 4-year OS after BMT was not statistically different between MRD and URD recipients. This study shows that the outcomes of pediatric patients transplanted for SAA with a URD in Brazil are approaching those of MRD transplants. In contrast, OS after MRD BMT was lower than we would expect based on previous reports. The wide range of preparatory regimens used by the study centers highlights the need for standardized protocols for these children. Our findings provide a benchmark for future studies focused on improving BMT outcomes in this setting in Brazil.

Aplastic Anemia Preconditioned with Fludarabine, Cyclophosphamide, and Anti-Thymocyte Globulin

Background

Graft rejection and graft versus host disease (GvHD) have impeded the success of hematopoietic cell transplantation for severe aplastic anemia (SAA) patients. There is no sufficient data to identify the outcomes of peripheral blood stem cell transplantation (PBSCT) in SAA patients, especially for adult SAA patients. The aim of this study was to evaluate the outcomes of adult SAA patients undergoing PBSCT with the FCA regimen. The FCA regimen includes fludarabine, cyclophosphamide, and anti-thymocyte globulin (ATG).

Material/Methods

We report our experience with 46 adult SAA patients who underwent PBSCT with the FCA regimen. Thirty SAA patients who received only cyclophosphamide and ATG (CA) regimen were used as controls. Complications and survival outcomes were evaluated and compared.

Results

There was a significantly higher percentage of patients who achieved >95% donor chimerism by day 30 in the FCA group. The 5-year event-free survival (EFS) rate in the FCA group was higher than that in the CA group (95.4% versus 73.3%). In addition, the 5-year rejection rate (RR) in the FCA group was lower than that in the CA group (4.6% versus 23.6%). A multivariable model identified the FCA regimen as an independent factor affecting EFS and RR. However, GvHD and serious infection did not differ between the 2 groups. For patients with an unrelated donor, the FCA regimen had a higher EFS and a lower RR than the CA regimen.

Conclusions

The FCA regimen for PBSCT in adult SAA patients compared favorably to the CA regimen. It can improve EFS and reduce graft rejection, especially for unrelated donor PBSCT.

The Case for Upfront HLA-Matched Unrelated Donor Hematopoietic Stem Cell Transplantation as a Curative Option for Adult Acquired Severe Aplastic Anemia

The improved success of HLA-matched unrelated donor (MUD) hematopoietic stem cell transplantation (HSCT) for severe aplastic anemia (SAA) in recent decades has had an impact on the indications for and timing of this treatment modality. In the absence of a matched sibling donor (MSD), historically MUD HSCT was reserved as an option after failure to respond to at least 2 courses of immunosuppressive therapy (IST) in adults with SAA, but with improved outcomes over time, it is now considered following failure to respond to 1 course of IST. Recent national and international studies and guidelines now recommend upfront MUD HSCT as an option for children for whom an MUD is readily available, because outcomes are similar to those for MSD HSCT. Fludarabine-based conditioning and the use of in vivo T cell depletion with antithymocyte globulin or alemtuzumab has been associated with a reported overall survival (OS) of >85% in adult patients undergoing MUD HSCT. However, the recent introduction of eltrombopag for patients with SAA has transformed the treatment landscape, and there is currently much interest in its use with IST as upfront treatment, which showed a high response rate in an early-phase study. The risks of HSCT, especially graft-versus-host disease (GVHD), need to be carefully balanced against the concerns of IST, namely relapse and later clonal evolution to myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML). In the absence of a current prospective randomized trial comparing these 2 approaches, in this review we examine the evidence supporting consideration of early MUD HSCT in adults with SAA who would have been considered for MSD HSCT but who lack a MSD and for whom an MUD is readily available, especially using an irradiation-free conditioning regimen, with a low risk of GVHD, as another treatment option. This option may be offered to patients to provide them with an informed choice, with the aim of curing disease rather than achieving freedom from disease, relapse-free survival, or OS. Furthermore, understanding the immune signature for the response to IST and the immunologic responses to somatic mutations and clonal progression to MDS/AML may help define the future indications for upfront HSCT and a more precise medical approach to therapy.

Comparable Outcomes of First-Line Hematopoietic Stem Cell Transplantation from Unrelated and Matched Sibling Donors in Adult Patients with Aplastic Anemia: A Retrospective Single-Center Study

To explore the feasibility of upfront unrelated donor (URD) hematopoietic stem cell transplantation (HSCT) in the treatment of adult aplastic anemia (AA), we conducted a retrospective, single-center study and compared the outcomes of adult patients who underwent first-line URD HSCT or matched sibling donor (MSD) HSCT between August 2012 and June 2018. In all, 23 URD HSCT recipients had an increased cumulative incidence of grade II acute graft-versus-host disease (aGVHD) (21.7% versus 3.4%; P =.007), but similar rates of secondary graft failure (8.7 ± 6.0% versus 6.9 ± 3.4%; P = .764), chronic GVHD (cGVHD) (18.2% versus 8.8%; P = .285), extensive cGVHD (9.1% versus 3.5%; P = .328), 5-year estimated overall survival (87.0% versus 94.2%; P = .501), and 5-year estimated failure-free survival (82.0% versus 89.3%; P = .404) compared with 58 MSD HSCT recipients treated during the same period. After using propensity score matching to reduce the influence of potential confounders, the 2 groups were well balanced in terms of pretransplantation clinical factors. The median survival time was similar, and no significant differences in the aforementioned outcomes were observed between the 2 groups. Our results suggest that URD HSCT may be an effective and feasible option for first-line therapy in adult AA patients who lack an MSD.

Aplastic Anemia & MDS International Foundation (AA&MDSIF): Bone Marrow Failure Disease Scientific Symposium 2018

The bone marrow failure (BMF) syndromes are a group of rare disorders characterized by ineffective hematopoiesis resulting from deficiencies in the hematopoietic stem cell compartment. Although these diseases are typically acquired, some forms (e.g., Fanconi anemia, dyskeratosis congenita, Diamond Blackfan anemia, and Shwachman Diamond syndrome) are inherited. Patients with BMF syndromes can develop peripheral blood cytopenias and pancytopenia, and their disease can ultimately progress to acute myelogenous leukemia (AML). Research around the world is shedding light on the biology of the BMF syndromes, their clinical effects, and novel treatments. The Aplastic Anemia and MDS International Foundation (AAMDSIF) is an independent nonprofit organization whose mission is to help patients and family members cope with BMF syndromes. This report summarizes presentations on the latest scientific discoveries in BMF syndromes from the Sixth International Bone Marrow Failure Disease Scientific Symposium sponsored by AAMDSIF on March 22-23, 2018, in Rockville, Maryland.

Unmanipulated Haploidentical Hematopoietic Stem Cell Transplantation Achieved Outcomes Comparable With Matched Unrelated Donor Transplantation in Young Acquired Severe Aplastic Anemia

Salvage haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is considered in patients with severe aplastic anemia (SAA) if a matched unrelated donor (MUD) is unavailable. However, studies on haplo- and MUD transplantation in SAA are lacking. The present study retrospectively analyzed the outcomes of 89 young SAA patients who underwent unmanipulated alternative HSCT between September 2012 and September 2016 at our single center. Forty-one patients received haploidentical donors and forty-eight patients MUDs for HSCT. Most were heavily transfused and refractory to previous immunotherapy. The median durations for myeloid engraftment in the haplo- and MUD cohorts were 14 (range, 10 to 21) and 13 (range, 10 to 18) days, respectively. Compared with the MUD cohort, haplo-HSCT cohorts had an increased cumulative incidence of acute graft-versus-host disease (GVHD) grades II to IV (43.9% ± 7.8% versus 12.5% ± 4.8%, P = .001) and grades III to IV (21.1% ± 6.7% versus 6.6% ± 3.7%, P = .045) and similar limited chronic GVHD (47.7% ± 8.5% versus 38.5% ± 7.3%, P = .129) and extensive chronic GVHD (12.1% ± 6.8% versus 9.1% ± 4.3%, P = .198). The median follow-up time of the surviving patients was 26 months (range, 6 to 45). No significant differences were observed between haplo-HSCT and MUD HSCT cohorts in 3-year overall survival (80.3% ± 5.1% versus 89.6% ± 7.0%, P = .210), disease-free survival (76.4% ± 5.1% versus 89.4% ± 7.7%, P = .127), and GVHD-free failure-free survival (79.0% ± 8.6% versus 71.6% ± 9.3%, P = .976). Thus, haplo-HSCT, as salvage therapy, achieved similar outcomes as MUD HSCT in young SAA patients, thereby rendering it as an effective and safe option for SAA.

Allogeneic Matched Related Donor Bone Marrow Transplantation for Pediatric Patients With Severe Aplastic Anemia Using "Low-dose" Cyclophosphamide, ATG Plus Fludarabine

BACKGROUND

The combination of cyclophosphamide (CY) and antithymocyte globulin (ATG) has been used as a standard conditioning regimen for matched related donor transplantation in patients with severe aplastic anemia.

PROCEDURE

To decrease the regimen-related toxicity while maintaining appropriate engraftment and survival rates, fludarabine (FLU) was added to the regimen. Four pediatric patients received matched related donor bone marrow transplantation with CY (50 mg/kg×2) (instead of the 50 mg/kg×4 standard dosing), equine ATG (30 mg/kg×3), with the addition of FLU (30 mg/m×4). Graft versus host disease (GvHD) prophylaxis included a calcineurin inhibitor and methotrexate.

RESULTS

No grade 4 acute toxicities occurred during the first 30 days after transplant. All patients engrafted with normalization of peripheral blood counts and transfusion independence. One patient developed grade 1 to 2 acute GvHD, followed by chronic GvHD that resolved. With a median follow-up of 41.7 months, all 4 patients are alive and transfusion free, with complete donor chimerism. This combination of a low-dose CY/ATG+FLU regimen was overall very well tolerated and contributed toward a successful outcome including engraftment, chimerism, and survival.

CONCLUSION

This small pilot study shows that this cytoreductive regimen could be considered as the standard of care for transplantation of pediatric patients with aplastic anemia from HLA-matched siblings.

Hematopoietic cell transplantation for aplastic anemia

PURPOSE OF REVIEW

Improvements in allogeneic hematopoietic cell transplantation (HCT) with better donor selection, conditioning regimens and graft vs. host disease prophylaxis make it reasonable to move HCT earlier in the algorithm for management of severe aplastic anemia (SAA). Recent progress in transplantation is reviewed whereas issues related to developing countries are also addressed.

RECENT FINDINGS

Multiple research centers are reporting on clonality, mutations and telomere disorders in SAA, which may help to choose the most appropriate therapy upfront. Eltrombopag, in combination with immunosuppressive therapy (IST), has shown remarkable improvement over historical IST, and long-term follow-up is awaited. In younger patients and in experienced centers, matched unrelated-donor (MUD) and related haploidentical transplants (haplo-HCT) are being reported with survival approaching that seen with sibling transplants. Literature from resource-limited countries highlight the need to modify guidelines to make them affordable and cost-effective. Bone marrow remains the graft source of choice; peripheral blood stem cells may be acceptable in special circumstances in resource-constrained countries.

SUMMARY

The potential of novel research findings and new therapeutic trials should be maximized by validation in different centers, countries and patient populations to provide personalized care to patients with aplastic anemia.

Outcomes and healthcare utilization in children and young adults with aplastic anemia: A multiinstitutional analysis

BACKGROUND

Aplastic anemia is a bone marrow failure syndrome with high mortality affecting children and young adults. Although current treatment guidelines recommend hematopoietic stem cell transplant (HCT) for patients with matched sibling donors, outcomes with alternate donor options have been improving.

PROCEDURE

We analyzed a validated multiinstitutional pediatric cohort using one of the largest pediatric and young adult database, the Pediatric Health Information System, for patients diagnosed with aplastic anemia (AA) from 2006 to 2015. Outcomes with upfront and salvage transplants were analyzed along with healthcare utilization.

RESULTS

Among 2,169 patients in the study period, almost 20% underwent HCT, while others received immunosuppressive therapy. In a multivariate model, there was no significant difference in mortality with upfront or salvage transplants (odds ratio [OR] 1.24, 95% confidence interval [CI] 0.6-2.58, P = 0.567), while every platelet transfusion was associated with higher mortality (OR 1.37, 95% CI 1.12-1.67, P = 0.002). Healthcare utilization was significantly higher in salvage transplants requiring frequent hospitalization and transfusion requirements. Treatment mortality and graft failure rates were significantly reduced in the salvage transplant group in recent years (2011-2015 as compared to 2006-2010).

CONCLUSION

As outcomes with HCT continue to improve in severe AA, transplant with good alternate donors should be considered upfront in children and young adults.

Fludarabine-based reduced intensity regimen for matched related donor hematopoietic stem cell transplantation in acquired severe aplastic anemia

Different conditioning regimens have been evaluated in matched-related donor allogeneic hematopoietic stem cell transplantation (allo-HSCT) for acquired severe aplastic anemia (SAA) with varying results. In this manuscript, we report our experience with fludarabine (120mg/m²), very low dose cyclophosphamide (1200mg/m²) and antithymocyte globulin (7.5mg/kg). Low dose total body irradiation (2Gy) was added to the conditioning regimen for patients older than 15 years. Nineteen patients (median age 23years) underwent transplant between 2008 and 2015. The majority (89%) were younger than 40 years. Stem cell source was BM (n=11) or PBSC (n=8). GvHD prophylaxis consisted of cyclosporine and either a short course of methotrexate (n=9) or mycophenolate mofetil (n=10). Eighteen (94.7%) patients achieved sustained engraftment. The median times to neutrophil and platelet engraftments were 19 (range: 14-34) and 17.1 (range: 12-25) days, respectively. The day-30 cumulative incidence of neutrophil and platelet engraftment was 89.4% and 94.7%, respectively. No secondary graft rejection was observed. The 1-year cumulative incidence of aGvHD (grade II-IV) and cGvHD was 11.7% and 0%, respectively. The 2-year GvHD-free survival rate was 78.6% (95% CI: 52.5-91.4%). Fludarabine-based reduced intensity regimen for MRD allo-HSCT in SAA compares favorably to other available regimens. This regimen deserves further investigations with larger cohort of patients.

Improved outcome of haploidentical transplantation in severe aplastic anemia using reduced-intensity fludarabine-based conditioning

Significant improvements in hematopoietic stem cell transplantation (HSCT) with haploidentical family donors (HFD) have confirmed its therapeutic role in severe aplastic anemia (SAA) and led to the evolution of treatment algorithms. However, the optimal conditioning regimen for HFD-HSCT remains undefined, especially the dosage of cyclophosphamide (Cy). A total of 77 patients with SAA from two research centers, who received HFD-HSCT with reduced-intensity fludarabine + cyclophosphamide + thymoglobulin ± busulfan conditioning regimen plus third-party cells infusion were included in this study, of which 67 pairs had 4-5 loci mismatched. We were particularly interested in whether the dosage of Cy significantly impacted graft failure (GF) and overall survival (OS). All patients showed sustained hematopoietic engraftment without any increase in severe aGVHD and transplantation-related mortality (TRM). The incidences of grade II-IV aGVHD, grade III-IV aGVHD and extensive cGVHD were 18%, 10% and 7%, respectively. The probabilities of 1-year and 5-year OS were 93.1% and 87.9%, respectively. Furthermore, patient age <15 years, MNC cells >8×10⁸/kg and donor age <45 years were associated with better survival (P=0.043, P=0.023, and P=0.037, respectively) and engraftment (P=0.019, P=0.008, and P=0.001, respectively). Our findings indicated that SAA patients lack MSD benefited the most if HFD-HSCT was performed with reduced-intensity fludarabine-based conditioning regimen. Improved outcomes with HFD-HSCT may lead to a salvaged therapy and an expanded direct role for SAA in the future.

Beneficial Role of Low-Dose Antithymocyte Globulin in Unrelated Stem Cell Transplantation for Adult Patients with Acquired Severe Aplastic Anemia: Reduction of Graft-versus-Host Disease and Improvement of Graft-versus-Host Disease-Free, Failure-Free Survival Rate

Stem cell transplantation (SCT) from an unrelated donor (URD) is often considered in patients with severe aplastic anemia (SAA) whom immunosuppressive therapy failed and matched sibling donor is not available. To reduce the incidence of graft-versus-host disease (GVHD) in URD SCT, introducting antithymocyte globulin (ATG) into the conditioning regimen has been proposed. Although ATG was shown to play a role in reducing GVHD in a cohort with diverse hematologic diseases, its role in SAA remains uncertain. The aim of this study was to determine the efficacy and toxicity of ATG in URD SCT for adult patients with SAA. We investigated 83 adult patients with SAA who underwent URD SCT between 2003 and 2014. The transplantation strategy consisted of total body irradiation (total 800 cGy) and cyclophosphamide (total 100 mg/kg to 120 mg/kg), followed by tacrolimus and a short-term methotrexate. We divided patients into 2 groups: group 1 (n = 25), which received HLA-matched (8/8) bone marrow (BM) without ATG, and group 2 (n = 58), which received SCT from either an HLA-mismatched donor or peripheral blood (PB). Thereafter, group 2 was subdivided according to ATG use into group 2A (without ATG, n = 26), which served as a historical cohort, and group 2B (with ATG, n = 32). Rabbit ATG (Thymoglobulin; Genzyme-Sanofi, Lyon, France) was used in group 2B at a dose of 2.5 mg/kg. The median age of all patients was 30 years (range, 17 to 59 years). The incidence of GVHD was significantly lower in group 2B than group 2A, as demonstrated by the rate of grade II to IV acute GVHD at day 100 (31.2% versus 61.5%, P = .003) and the rate of chronic GVHD at 3 years (21.9% versus 65.4%, P = .002). The overall survival rates of the 3 groups were similar. However, GVHD-free, failure-free survival (GFFS) was significantly higher in group 2B than group 2A (P = .034). A multivariable model identified use of ATG as an independent factor affecting grades II to IV acute GVHD (hazard ratio [HR], 2.902; 95% confidence interval [CI], 1.417 to 5.942; P = .004), chronic GVHD (HR , 3.005; 95% CI, 1.279 to 7.059; P = .012), and GFFS (HR, 2.363; 95% CI, 1.162 to 4.805; P = .014). Toxicities, including infectious complications, were not different among the 3 groups. In conclusion, low-dose ATG (2.5 mg/kg) can reduce the incidence of acute and chronic GVHD and improve the quality of life in patients with SAA who receive stem cells from either an HLA-mismatched donor or PB; importantly, these benefits are achieved without increased toxicity. Furthermore, ATG can be considered in URD SCT from HLA-matched BM cells.

Pharmacokinetic comparison of cyclosporin A and tacrolimus in graft-versus-host disease prophylaxis

A number of studies were published with contradictory results comparing tacrolimus (Tac) and cyclosporine A (CsA) for graft-versus-host disease (GVHD) prophylaxis, but there are only few that accounted for pharmacokinetic (PK) parameters. In this study, we created a model based on median concentrations, variability of concentrations, and failures to maintain target levels that distinguished patients with low, intermediate, and high risks of acute GVHD (hazard ratios (HR) 1.77, 95%CI 1.36-2.32, p < 0.0001). This model was used to compare 95 patients with CsA and 239 with Tac GVHD prophylaxis. In the multivariate analysis, incorporating PK risk, no differences were observed for grade II-IV acute GVHD (HR 0.73, 95%CI 0.48-1.10, p = 0.13), but grade III-IV acute GVHD was lower in the Tac group (HR 0.47, 95%CI 0.28-0.78, p = 0.004). The observed difference was due to patients with high PK risk (HR 0.377, 95%CI 0.19-0.75, p = 0.005), but not with low and intermediate PK risk (p > 0.05). Patients in the Tac group had better GVHD relapse-free survival (HR = 0.659, p = 0.01) and comparable overall survival (p > 0.05). In conclusion, PK risk should be accounted for in comparisons of GVHD prophylaxis regimens with calcineurin inhibitors, and Tac was superior to CsA in patients with high, but not intermediate and low PK risk.

Immunosuppressive therapy versus alternative donor hematopoietic stem cell transplantation for children with severe aplastic anemia who lack an HLA-matched familial donor

We compared the outcomes of immunosuppressive treatment (IST) with those of alternative donor hematopoietic stem cell transplantation (HSCT) in children and adolescents with severe aplastic anemia (SAA). The medical records of 42 patients with SAA who received frontline IST (N=19) or frontline HSCT with an alternative donor (N=23) between 1998 and 2012 were analyzed retrospectively. Six patients responded in the frontline IST group, whereas 11 underwent salvage HSCT after IST failure. Twenty-one of 23 patients who underwent frontline HSCT survived without treatment failure. The estimated failure-free survival rate of the frontline HSCT group was higher than that of the frontline IST group (91.3% vs 30.7% respectively, P<0.001). Six of 11 patients who underwent salvage HSCT experienced event-free survival (EFS). The estimated EFS of the frontline HSCT group was higher than that of the salvage HSCT group (91.3% vs 50.9% respectively, P=0.015). The outcome of alternative donor HSCT was better than commonly reported rates, especially in patients who underwent frontline HSCT. These results suggest that frontline alternative donor HSCT may be a better treatment option than IST for children and adolescents with SAA who lack a human leukocyte Ag-matched familial donor.

Unrelated alternative donor transplantation for severe acquired aplastic anemia: a study from the French Society of Bone Marrow Transplantation and Cell Therapies and the EBMT Severe Aplastic Anemia Working Party

Unrelated allogeneic transplantation for severe aplastic anemia is a treatment option after immunosuppressive treatment failure in the absence of a matched sibling donor. Age, delay between disease diagnosis and transplantation, and HLA matching are the key factors in transplantation decisions, but their combined impact on patient outcomes remains unclear. Using the French Society of Bone Marrow Transplantation and Cell Therapies registry, we analyzed all consecutive patients (n=139) who underwent a first allogeneic transplantation for idiopathic severe aplastic anemia from an unrelated donor between 2000 and 2012. In an adjusted multivariate model, age over 30 years (Hazard Ratio=2.39; P=0.011), time from diagnosis to transplantation over 12 months (Hazard Ratio=2.18; P=0.027) and the use of a 9/10 mismatched unrelated donor (Hazard Ratio=2.14; P=0.036) were independent risk factors that significantly worsened overall survival. Accordingly, we built a predictive score using these three parameters, considering patients at low (zero or one risk factors, n=94) or high (two or three risk factors, n=45) risk. High-risk patients had significantly shorter survival (Hazard Ratio=3.04; P<0.001). The score was then confirmed on an independent cohort from the European Group for Blood and Marrow Transplantation database of 296 patients, with shorter survival in patients with at least 2 risk factors (Hazard Ratio=2.13; P=0.005) In conclusion, a simple score using age, transplantation timing and HLA matching would appear useful to help physicians in the daily care of patients with severe aplastic anemia.

Acquired aplastic anemia in Korean children: treatment guidelines from the Bone Marrow Failure Committee of the Korean Society of Pediatric Hematology Oncology

The treatment of choice for aplastic anemia (AA) in children has been HLA-matched family donor (MFD) hematopoietic stem cell transplantation (HSCT). For those lacking MFD, immunosuppressive therapy (IST) consisting of horse antithymocyte globulin (ATG) and cyclosporine has been successful. The choices of second and third line treatments are more complex and debatable, especially in the situation of unavailability of horse ATG. IST with rabbit ATG seems to be less effective. Recently, improved survival of non-MFD HSCTs has been documented. The outcome of matched or mismatched unrelated donor, umbilical cord blood, or haploidentical family donor transplantations will be discussed in AA children after IST failure. Experimental approaches of upfront HSCT using non-MFDs will be briefly touched. In this review, a treatment guideline for children with AA from the Korean Society of Pediatric Hematology Oncology will be presented along with a brief review of literature on current clinical practices in Korea.

Evolving hematopoietic stem cell transplantation strategies in severe aplastic anemia

PURPOSE OF REVIEW

Significant improvements in unrelated donor hematopoietic stem cell transplantation (HSCT) in recent years have solidified its therapeutic role in severe aplastic anemia (SAA) and led to the evolution of treatment algorithms, particularly for children.

RECENT FINDINGS

Advances in understanding the genetics of inherited bone marrow failure syndromes (IBMFS) have allowed more confidence in accurately diagnosing SAA and avoiding treatments that could be dangerous and ineffective in individuals with IBMFS, which can be diagnosed in 10-20% of children presenting with a picture of SAA. Additionally long-term survival after matched sibling donor and matched unrelated donor HSCT now exceed 90% in children. Late effects after HSCT for SAA are minimal with current strategies, and compare favorably to late effects after upfront immunosuppressive therapy, except for patients with chronic graft versus host disease.

SUMMARY

Careful assessment for signs or symptoms of IBMFS, along with genetic screening for these disorders, is of major importance. Matched sibling donor HSCT is already considered the standard of care for upfront therapy and some groups are evaluating matched unrelated donor HSCT as primary therapy. Ongoing studies will continue to challenge treatment algorithms and may lead to an even more expanded role for HSCT in SAA.

Comparing Outcomes with Bone Marrow or Peripheral Blood Stem Cells as Graft Source for Matched Sibling Transplants in Severe Aplastic Anemia across Different Economic Regions

Bone marrow (BM) is the preferred graft source for hematopoietic stem cell transplantation (HSCT) in severe aplastic anemia (SAA) compared with mobilized peripheral blood stem cells (PBSCs). We hypothesized that this recommendation may not apply to those regions where patients present later in their disease course, with heavier transfusion load and with higher graft failure rates. Patients with SAA who received HSCT from an HLA-matched sibling donor from 1995 to 2009 and reported to the Center for International Blood and Marrow Transplant Research or the Japan Society for Hematopoietic Cell Transplantation were analyzed. The study population was categorized by gross national income per capita and region/countries into 4 groups. Groups analyzed were high-income countries (HIC), which were further divided into United States-Canada (n = 486) and other HIC (n = 1264); upper middle income (UMIC) (n = 482); and combined lower-middle, low-income countries (LM-LIC) (n = 142). In multivariate analysis, overall survival (OS) was highest with BM as graft source in HIC compared with PBSCs in all countries or BM in UMIC or LM-LIC (P < .001). There was no significant difference in OS between BM and PBSCs in UMIC (P = .32) or LM-LIC (P = .23). In LM-LIC the 28-day neutrophil engraftment was higher with PBSCs compared with BM (97% versus 77%, P = .002). Chronic graft-versus-host disease was significantly higher with PBSCs in all groups. Whereas BM should definitely be the preferred graft source for HLA-matched sibling HSCT in SAA, PBSCs may be an acceptable alternative in countries with limited resources when treating patients at high risk of graft failure and infective complications.

Current management of severe acquired aplastic anemia

Overall survival in severe aplastic anemia has markedly improved in the past four decades due to advances in stem cell transplantation, immunosuppressive therapies and supportive care. Horse anti-thymocyte globulin plus cyclosporine is the standard immunosuppressive regimen in severe aplastic anemia, and often employed as initial therapy as most are not candidates for a matched related stem cell transplantation. With this regimen, hematologic response can be achieved in 60 to 70% of cases, but relapse is observed in 30 to 40% of responders and clonal evolution in 10 to 15% of patients. Efforts to improve outcomes beyond horse anti-thymocyte globulin plus cyclosporine have been disappointing, with no significant improvement in the critical parameter of hematologic response, which strongly correlates with long-term survival in severe aplastic anemia. Furthermore, rates of relapse and clonal evolution have also not improved with the development of three drug regimens or with more lymphocytotoxic therapies. Therefore, horse anti-thymocyte globulin plus cyclosporine remains the standard immunosuppression of choice as first therapy in severe aplastic anemia. Interestingly, survival has markedly improved over the years in large part due to better anti-infective therapy and more successful salvage therapies with immunosuppression and stem cell transplantation. In this review general aspects of diagnosis and management are discussed.

Cyclophosphamide conditioning in patients with severe aplastic anaemia given unrelated marrow transplantation: a phase 1-2 dose de-escalation study

BACKGROUND

The optimum preparative regimen for unrelated donor marrow transplantation in patients with severe aplastic anaemia remains to be established. We investigated whether the combination of fludarabine, anti-thymocyte globulin, and total body irradiation (TBI) would enable reduction of the cyclophosphamide dose to less than 200 mg/kg while maintaining engraftment and having a survival similar to or better than that with standard regimens using a cyclophosphamide dose of 200 mg/kg (known to be associated with significant organ toxicity) for unrelated donor transplantation for severe aplastic anaemia. We have previously shown that cyclophosphamide at 150 mg/kg resulted in excess toxicity and its omission (0 mg/kg) resulted in unacceptable graft failure (three of three patients had secondary graft failure). Here we report results for the 50 mg/kg and 100 mg/kg cohorts.

METHODS

In a multicentre phase 1-2 study, patients (aged ≤65 years) with severe aplastic anaemia, adequate organ function, and an unrelated adult marrow donor HLA matched at the allele level for HLA A, B, C, and DRB1 or mismatched at a single HLA locus received bone marrow grafts from unrelated donors. All patients received anti-thymocyte globulin (rabbit derived 3 mg/kg per day, intravenously, on days -4 to -2, or equine derived 30 mg/kg per day, intravenously, on days -4 to -2), fludarabine (30 mg/m(2) per day, intravenously, on days -5 to -2), and TBI (2 Gy). Cyclophosphamide dosing started at 150 mg/kg and was de-escalated in steps of 50 mg/kg (to 100 mg/kg, 50 mg/kg, and 0 mg/kg). The primary endpoint was the selection of the optimum cyclophosphamide dose based on assessments of graft failure (primary or secondary), toxicity, and early death during 100 days of follow-up after the transplant; this is the planned final analysis for the primary endpoint. This trial is registered with ClinicalTrials.gov, number NCT00326417.

FINDINGS

96 patients had bone marrow transplant. At day 100, 35 (92%) of 38 patients were engrafted and alive in the cyclophosphamide 50 mg/kg cohort and 35 (85%) of 41 in the 100 mg/kg cohort. Cyclophosphamide 50 mg/kg and 100 mg/kg resulted in posterior means for fatality without graft failure of 0·7% (credible interval 0-3·3) and 1·4% (0-4·9), respectively. Three patients (8%) had graft failure with cyclophosphamide 50 mg/kg and six (15%) with cyclophosphamide 100 mg/kg. Four (11%) patients had major regimen-related toxicity with cyclophosphamide 50 mg/kg and nine (22%) with cyclophosphamide 100 mg/kg. The most common organ toxicity was pulmonary (grade 3 or 4 dyspnoea or hypoxia including mechanical ventilation), and occurred in three (8%) and four (10%) patients given cyclophosphamide 50 mg/kg and 100 mg/kg, respectively.

INTERPRETATION

Cyclophosphamide at 50 mg/kg and 100 mg/kg with TBI 2 Gy, fludarabine, and anti-thymocyte globulin results in effective conditioning and few early deaths after unrelated donor transplantation for severe aplastic anaemia. These doses of cyclophosphamide provide a framework for further regimen optimisation strategies.

FUNDING

US National Heart, Lung, and Blood Institute and National Cancer Institute.

Second allogeneic stem cell transplant for aplastic anaemia: a retrospective study by the Severe Aplastic Anaemia Working Party of the European Society for Blood and Marrow Transplantation

We analysed the outcome of a second allogeneic haematopoietic stem cell transplant (alloHSCT) in 162 patients reported to the European Society for Blood and Marrow Transplantation between 1998 and 2009. Donor origin was a sibling in 110 and an unrelated donor in 52 transplants, respectively. The stem cell source was bone marrow in 31% and peripheral blood in 69% of transplants. The same donor as for the first alloHSCT was used in 81% of transplants whereas a change in the choice of stem cell source was reported in 56% of patients, mainly from bone marrow to peripheral blood. Neutrophil and platelet engraftment occurred in 85% and 72% of patients, after a median time of 15 and 17 days, respectively. Grade II-IV acute graft-versus-host disease (GVHD) and chronic GVHD occurred in 21% and 37% of patients, respectively. Graft failure (GF) occurred in 42 patients (26%). After a median follow-up of 3·5 years, the 5-year overall survival (OS) was 60·7%. In multivariate analysis, the only factor significantly associated with a better outcome was a Karnofsky/Lansky score ≥80 (higher OS). We conclude that a second alloHSCT is feasible rescue option for GF in SAA, with a successful outcome in 60% of cases.

Immunosuppressive therapy for transplant-ineligible aplastic anemia patients

Aplastic anemia is a rare life-threatening bone marrow failure that is characterized by bicytopenia or pancytopenia in the peripheral blood and a hypoplastic or aplastic bone marrow. The patients are at risk of infection and hemorrhage due to neutropenia and thrombocytopenia and suffer from symptoms of anemia. The main treatment approaches are allogeneic stem cell transplantation and immunosuppression. Here, we review current standard immunosuppression and the attempts that have been made in the past two decades to improve results: review of recent developments also reveals that sometimes not only the advent of new drugs, good ideas and well-designed clinical trials decide the progress in the field but also marketing considerations of pharmaceutical companies. Aplastic anemia experts unfortunately had to face the situation that efficient drugs were withdrawn simply for marketing considerations. We will discuss the current options and challenges in first-line treatment and management of relapsing and refractory patients with an emphasis on adult patients. Some promising new approaches are currently under investigation in prospective, randomized trials.

The diagnosis and treatment of aplastic anemia: a review

Aplastic anemia is a rare disorder characterized by suppression of bone marrow function resulting in progressive pancytopenia. A trigger-related abnormal T cell response facilitated by some genetic predisposition has been postulated as the pathogenetic mechanism leading to the overproduction of bone marrow-inhibiting cytokines. Immuno-mediated pathogenesis is confirmed by the response to immunosuppressive treatment (IST) (cyclosporin A+ATG), which represents the first-choice therapy for patients <40 years when a matched sibling donor (MSD) is not available for transplant. MSD hematopoietic stem cell transplantation (HSCT) is associated with cure in ~90 % of patients. IST up-front provides an overall survival (OS) rate of above 90 %, but a response rate of about 60 %. Front-line matched unrelated donor (MUD) appears to be a viable option in children with similar OS and event-free survival to that in MSD HSCT. MUD HSCT post-IST failure proved to be a very good rescue strategy. Haploidentical donors/cord blood transplants or alternative immunosuppressive therapies, such as alemtuzumab, may represent valid tools for resistant/relapsing cases. New promising strategies, such as eltrombopag, are now under investigation. Patients should be offered an accurate diagnostic work-up in order to rule out other underlying disorders, primarily constitutional marrow failures, which may require different approaches.

Current outcome of HLA identical sibling versus unrelated donor transplants in severe aplastic anemia: an EBMT analysis

We have analyzed 1448 patients with acquired aplastic anemia grafted between 2005 and 2009, and compared outcome of identical sibling (n=940) versus unrelated donor (n=508) transplants. When compared to the latter, sibling transplants were less likely to be performed beyond 180 days from diagnosis (39% vs. 85%), to have a cytomegalovirus negative donor/recipient status (15% vs. 23%), to receive antithymocyte globulin in the conditioning (52% vs. 61%), and more frequently received marrow as a stem cell source (60% vs. 52%). Unrelated donor grafts had significantly more acute grade II-IV (25% vs. 13%) and significantly more chronic graft-versus-host disease (26% vs. 14%). In multivariate analysis, the risk of death of unrelated donor grafts was higher, but not significantly higher, compared to a sibling donor (P=0.16). The strongest negative predictor of survival was the use of peripheral blood as a stem cell source (P<0.00001), followed by an interval of diagnosis to transplant of 180 days or more (P=0.0005), patient age 20 years or over (P=0.0005), no antithymocyte globulin in the conditioning (P=0.003), and donor/recipient cytomegalovirus sero-status, other than negative/negative (P=0.04). In conclusion, in multivariate analysis, the outcome of unrelated donor transplants for acquired aplastic anemia, is currently not statistically inferior when compared to sibling transplants, although patients are at greater risk of acute and chronic graft-versus-host disease. The use of peripheral blood grafts remains the strongest negative predictor of survival.

Recent advances in treatment of aplastic anemia

Recent advances in the treatment of aplastic anemia (AA) made most of patients to expect to achieve a long-term survival. Allogeneic stem cell transplantation (SCT) from HLA-matched sibling donor (MSD-SCT) is a preferred first-line treatment option for younger patients with severe or very severe AA, whereas immunosuppressive treatment (IST) is an alternative option for others. Horse anti-thymocyte globuline (ATG) with cyclosporin A (CsA) had been a standard IST regimen with acceptable response rate. Recently, horse ATG had been not available and replaced with rabbit ATG in most countries. Subsequently, recent comparative studies showed that the outcomes of patients who received rabbit ATG/CsA were similar or inferior compared to those who received horse ATG/CsA. Therefore, further studies to improve the outcomes of IST, including additional eltrombopag, are necessary. On the other hand, the upper age limit of patients who are able to receive MSD-SCT as first-line treatment is a current issue because of favorable outcomes of MSD-SCT of older patients using fludarabine-based conditioning. In addition, further studies to improve the outcomes of patients who receive allogeneic SCT from alternative donors are needed. In this review, current issues and the newly emerging trends that may improve their outcomes in near futures will be discussed focusing the management of patients with AA.

Allogeneic hematopoietic cell transplantation without total body irradiation from unrelated donor in adult patients with idiopathic aplastic anemia: fludarabine versus cyclophosphamide-ATG

Total body irradiation (TBI) has traditionally been used in the conditioning regimen for allogenetic hematopoietic stem cell transplantation (alloHCT) from an unrelated donor (u-HCT). However, patients are increasingly receiving a fludarabine-based conditioning regimen without TBI, as it seemed less toxic than TBI. We need to know the clinical results of non-TBI u-HCT treatments. We retrospectively investigated the clinical outcomes of allogenetic hematopoietic cell transplantation (alloHCT) from an unrelated donor without TBI (non-TBI u-HCT) and compared the clinical outcomes of fludarabine-based (FLU group) and cyclophosphamide-ATG (Cy-ATG group) conditioning regimens. Sixty-one patients received the non-TBI conditioning regimen for u-HCT (32 in the FLU group and 29 in the Cy-ATG group). The cumulative incidence of neutrophil engraftment at 30 days, platelet>20K/μL at 30 days, acute graft-versus host disease (aGvHD) at 100 days, and chronic GvHD (cGvHD) at 2 years were 87.01%, 65.57%, 35.20%, and 26.64%, respectively. However, transplantation outcomes and overall survival rates did not differ between the FLU and Cy-ATG groups. Only infused CD34+ cells >3×10(6)kg(-1) was identified as a favorable factor for survival in the multivariate analysis. In conclusion, non-TBI u-HCT was feasible and there was no difference between the FLU and Cy-ATG groups in terms of transplantation outcomes.